Two companies responsible for "chronic and insidious" dirty dairying have failed to pay fines of $225,000 imposed by the Environment Court.

Official figures reveal that the number of abatement and infringement notices issued nearly doubled to 683 in the past year, across all councils.

Clear Ridge Station Ltd and Beejay Stud Ltd were convicted on multiple charges in Whangarei in October. Farms owned by the sister companies discharged a huge amount of untreated dairy effluent into the Manganui River, which feeds into the Wairoa River and the Kaipara Harbour.

Clear Ridge Station, which held 800-900 cows, was described as being "awash with dairy effluent", resulting in "gross contamination" of the river from multiple sources with the presence of pathogens such as campylobacter being "highly likely" and ammoniacal nitrogen levels 50 times above the toxicity threshold for invertebrates in the waterway.

Of the offending at Beejay Stud, Judge Craig Thompson said: "I can't recall any case as bad as this in terms of prolonged non-compliance. It was blatant, ongoing and serious".

Revelations of the breadth and seriousness of dairy pollution comes at a critical time a week out from the general election. Labour and National are locked in a battle over whether farmers should pay royalties for the waters they use to irrigate their farms, in order to help pay for the clean-up of polluted streams. On Monday, farmers are to march through Morrinsville, the Waikato hometown of Labour leader Jacinda Ardern, to protest her proposed water royalties.